1. Field of the Invention
This invention relates to a control system for an engine of a small watercraft, such as a personal watercraft, and more particularly to an engine ignition control system for such a watercraft.
2. Description of the Related Art
Internal combustion engines commonly include a spark advance system to control the time of initiating combustion in response to engine running conditions. The optimum time of spark plug firing for a given running condition enhances engine performance.
Optimum spark timing for an engine depends upon a variety of factors and primarily upon the load on the engine and the engine speed. Some spark advance systems also vary spark timing when sensing engine acceleration. Many types of conventional engine ignition systems include a spark advance mechanism that interrelates with the throttle valve of the engine so as to adjust spark timing in response to throttle valve position. The throttle valve position is directly related to the engine load. In some cases, the spark advance mechanisms are mechanical and include a linkage system that directly interconnects a throttle mechanism of the engine and the spark advance mechanism. U.S. Pat. No. 5,653,208 discloses an example of such a mechanical ignition control system. More advanced engines often employ electronic control systems that employ sensors to determine the running condition of the engine, and produce a firing signal to time the firing of the spark plugs in accordance with an ignition timing map stored in the memory of the control system. U.S. Pat. No. 5,775,297 discloses an example of an electronic ignition control system. In such a system, ignition timing varies upon whether rapid acceleration from idle to a high engine speed is detected.